Trigatron tube



1946' c. E. DAWLEY ETAL 75 TRIGATRON TUBE Filed Sept. 27, 1944 INVENTOR C: E 017W 5).

ATI'ORNEY Patented Dec. 24, 1946 UNITED STATES PATENT OFFICE TRIGATRON TUBE Clarence E. Dawley, Bloomfield, N. 1., assignmto Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application September 27, 1944, Serial No. 555,933

4 Claims. (or. 250-215) The present invention relates to discharge devices and more particularly to a triggered sparkgap device constituting an improvement over the structure shown and described in the copending application of E. G. F. Amott et al., Serial No. 491,496, filed September 19, 1943, assigned to the same assignee as the present invention, and of which I- am one of the coinventors.

The structure of the device as disclosed in such copending application comprises an envelope provided with three electrodes, one of which is a triggering electrode, and filled with a rare gas including a small percentage of oxygen and at an atmosphere or more pressure. A voltage is applied between two of the electrodes of insumcient magnitude to cause breakdown until a voltage is applied to the trigger electrode. Upon the application of the triggering voltage, an are dischargeoccurs between one of the high voltage electrodes and the triggering electrode since the latter is isolated from the other grounded high voltage electrode by suitable means such as a condenser.

Once such discharge is initiated between the high voltage electrode and the trigger electrode, the latter immediately assumes a high voltage and being positioned in such proximity to the grounded eiectrode, this high voltage on the trigger electrode causes the arc discharge to transfer to the grounded electrode enabling the passage of several hundred amperes between the high voltage electrode and ground.

The life of the device above noted is limited by several factors, namely, cleaning up of the oxygen forming part of the gaseous medium within the envelope, which occurs all through operating life of the device eventually decreasing the breakdown thereof below its useful operating voltage. Also due to the large current passing through the tube, sputtering of electrode material occurs which accumulates on the cathode and triggering electrodes causing a change in the electrode spacings, thereby altering the characteristics of the device.

The primary object of the present invention is to provide a device which eliminates the above I noted disadvantages, thus prolonging the useful life of a triggered spark-gap device.

Another object of thepresent invention is the provision of a triggered spark-gap device in which a fluid metal is employed as electrodes to eliminate sputtering of electrode material during the life of said device.

Another object of the present invention is the provision of a spark-gap device employing an inert gaseous filling so that "clean-up of the gas does not occur and liquid electrodes are provided to prevent sputtering during the useful life of the device.

Still further objects of the present invention will become obvious to those skilled in the art by reference to the accompanying drawing wherein:

Figure 1 .is a sectional view in elevation of a triggered spark-gap device constructed in accordance with the present invention, and

Figure 2 is a view similar to Fig. l of a modification which the triggered spark-gap of the present invention may take.

Referring now to the drawing in detail, the device as shown in Fig. 1 comprises an envelope shown generally at 5 composed in part of a vitreous material in the form of an annular collar 6, to the one end of which is sealed a spherical metallic member I having a coeflicient of expansion simulating that of the vitreous collar, such as the alloy known as Kovar. Also hermetically sealed to the other end of the vitreous collar 6 is a metallic flanged member 8 having an annular re-entrant portion 9, which is likewise formed of Kovar."

A metallic support Ill, which may be of Kovar if desired is provided with a spherical end I! concentric with the spherical member i, which is welded, soldered or otherwise aflixed at I3 to the reentrant portion 9 prior to sealing the metallic flanged member 8 to the vitreous collar 6. Although the metallic support i0 may be made long enough so as to provide an extension beyond the exterior surface of the flanged member 8. for assembly purposes it is preferable that it extend only a short distance into the reentrant portion 9 as shown, for reasons which will hereinafter appear.

An additional spherical metallic member formed of iron or steel and constituting the anode electrode ll of the device, is afllxed to a tubular member or support ii of Kovar, with such support being hermetically sealed to a reentrant portion IG of a vitreous flanged closure member ll. Hermetically sealed to the peripheral edge of such closure member is a "Kovar sleeve l8. After sealing the support l5 and the Kovar sleeve i8 to the vitreous closure member ll, the support l5 together with the anode i4 is inserted into the metallic support l0 and when the spherical anode i4 is concentrically disposed relative to the metallic spheres 1 and i2, the sleeve i8 is welded or soldered at l9 to the "Kovar flanged member 8. Thus this sleeve is 3 to all intents and purposes is an extension of the metallic support III.

The tubular support I5 is provided with an opening 20 which enables evacuation of the interior of the support l0, afterwhich it is filled with a quantity of liquid metal such as mercury 22 and an inert gas, such as a mixture of hydrogen and argon at a pressure ranging from approximately a hundred atmospheres to an atmosphere or less, prior to sealing-off the end 23 of the support l5. Similarly, the outer metallic spherical member i is provided with a tubulation 24 to allow evacuation of the space between its interior surface and that of the support in with its spherical end l2, after which it is filled with a small quantity of mercury or the like 25 and the same inert gas as above mentioned, prior to sealing-off the tubulation 24.

It will thus be seen that the various metallic parts are electrically insulated from each other by vitreous portions of the envelope but are readily accessible so as to enable the connection of electrical conductors thereto. The small quantity of mercury 25 in contact with the spherical end 1 constitutes the cathode electrode while the quantity of mercury 22 within the spherical end I2 is the trigger electrode properly isolated from ground and the sphere l4 the grounded anode. A high voltage is applied across the anode l4 and cathode 25 which is insufilcient to cause an arc discharge. Upon the application of a high voltage pulse of opposite sign to the trigger electrode 22, an arc discharge appears between the cathode 25 and the spherical end l2 supporting the mercury 22; and since the distance between the mercury pool 22 and the anode I4 is not sumcient to withstand the high voltage, the 'arc jump across to the grounded anode [4 thus completes the discharge from the cathode 25 to the anode l4.

By the utilization of concentric spheres, the mercury 22 and 25, which constitute in effect the electrode surfaces, can rotate within an angle of :90 from vertical with the device being fully operable from one of these extreme positions to the other. Moreover, the mercury does not sputter during operation as in devices of the prior art but volatilizes only, returning to the pool upon condensing. This, together with the employment of an inert gas which does not clean-up during operation, insure a relatively long useful life without variation in the operating characteristics due to a change in electrode spacing or gas pressure.

The modification as shown in Fig. 2 differs slightly from that of Fig. 1 in that it is of tandem construction being formed of two substantially identical devices joined together. In the main, the construction is similar to that of Fig. 1 since it includes an envelope shown generally at 30 and 32, and as each envelope is of identical structure, a detailed description of one should suifice.

The envelopes 30 and 32 are formed of a spherical metallic section 33 of Kovar or the like and hermetically sealed to a vitreous annular collar 34. Sealed to the opposite end of such vitreous collar 34 is a metallic flanged member 35 having a reentrant portion 36. Prior to scaling in the flanged member 35 to the collar 34, a metallic electrode support 31 i soldered or welded at 38 to the flanged member 35, with the outer end of the support 31 protruding above the surface of the flanged member and being threaded at 39 so as to engage an internally threaded metallic lug 40 secured to the metallic section 33 of the envelopes to enable them to be screwed together as shown in Fig. 2. As will be noted, the electrode support 31 has aiiixed to its lower end a spherical electrode 42 of iron or Kovar," which is concentrically disposed relative to the spherical section 33, and in like manner the upper envelope 32 has a spherical electrode 43 concentric with the spherical section 33 thereof. After evacuation of the envelopes 33 and 32, they are filled with an inert gas and a small quantity of mercury 44 and 45, respectively, prior to sealing-on at 45.

This modification operates in the identical manner as previously described-relative to Fig. 1 in that a high voltage is impressed across the spherical electrode 43 and the grounded spherical section 33 of envelope 30. Upon the application of a trigger pulse of opposite sign to electrode support 39 joining with the spherical metallic section of the envelope 3: and which is appropriately isolated from ground, an arc appears between the electrode 42 and the mercury pool 44. Inasmuch as electrode support 33 engages the lug 40 carried by the spherical metallic section 33 of envelope 32, the latter of which is contacted by the mercury pool 45 and hence may all be considered as one electrode, the full potential of electrode 44 appears on the mercury pool 45 and thus substantially simultaneously causes break down of the gap between the mercury 45 and spherical electrode 43 causing passage of energy completely through the device from electrode 43 to the metallic spherical section 33 of envelope 30. Like in Fig. 1 the modification of Fi 2 will operate in any position from to the vertical, and since the mercury 44 and 45 is struck by the arc discharge during operation, there is no sputtering of the electrode material, which would otherwise so accumulate as to alter the electrode spacing with change in the operating characteristics of the device.

It can thus be readily seen by those skilled in the art that a triggered spark-gap is herein provided in which sputtering of the electrode material is eliminated by the employment of a metallic liquid, such as mercury at the electrode surface impinged by the arc discharge, thus. presenting a variation in electrode spacing during operation of the device, which would otherwise affect the characteristics thereof. Moreover, by utilizing an inert gaseous environment in the device which presents clean-up of the ga together with the elimination of sputtering, the useful operating life of the device is considerably increased over similar devices of the prior art.

Although two embodiments of the present invention have been shown and described, it is to be understood that still further modification thereof may be made without departing from the spirit and scope of the appended claims.

I claim:

1. A spark-gap device for supporting a high voltage are discharge comprising an envelope provided with an inert gaseous medium and a plurality of concentrically disposed spaced spherical electrodes including an anode, a cathode, and a trigger electrode operable upon the application of a high voltage pulse thereto to cause an arc discharge between the trigger electrode and said cathode and an attendant substantially instantaneous initiation of an arc discharge with said anode; and a quantity of liquid metal in contact with said spherical trigger electrode and said spherical cathode respectively and constituting the surface of each electrode impinged by the resulting arc discharges. thus eliminating sputtering of electrode material otherwise occurring from the electrode surface impinged by the arc discharge with an attendant variation in electrode spacings and operating characteristics which destroy the useful life of the device.

2. A spark-gap device for supporting a high voltage arc discharge comprising an envelope provided with an inert gaseous medium and a plurality of concentrically disposed spaced spherical electrodes including an anode, a cathode, and a trigger electrode operable upon the application of a high voltage pulse thereto to cause an arc discharge between the tri ger electrode and said cathode and an attendant substantially instantaneous initiation of an arc discharge with said anode; and a quantity of mercury within said spherical trigger electrode and within said spherical cathode and constituting the surface of each electrode impinged bythe resulting arc discharges to eliminate sputtering of electrode material otherwise occurring from the electrode surface impinged by the arc discharges with an attendant variation in electrode spacings and operating characteristics which destroy the useful life of the device.

3. A spark-gap device for supporting a high voltage are discharge comprising an envelope provided with an inert gaseous medium therein and a plurality of concentrically disposed spaced spherical electrodes forming a portion of said envelope walls and hermetically sealed to vitreous insulating portions of said envelope, one of said electrodes constituting a trigger electrode operable upon the application of a high volttage pulse thereto to cause an arc discharge between said trigger electrode and another or said electrodes with substantially simultaneous initiation of an arc discharge between the remainder of said electrodes, and a quantity of liquid metal in contact with at least two of said spherical electrodes and constituting the surface of each said electrode impinged by the arc discharge during operation, thus eliminating sputtering of electrode material otherwise occurring from the electrode surface impinged by the arc discharge with an attendant variation in the electrode spacings and operating characteristics which destroy the useful life of the device.

4. A spark-gap device for supporting a high voltage arc discharge comprising an envelope provided with an inert gaseous medium therein and a plurality of concentrically disposed spaced spherical electrodes including an anode, a cathode, and a trigger electrode with said cathode and trigger electrode forming a portion of the envelope walls and hermetically sealed to vitreous insulating portions of said envelope; said trigger electrode being operable upon the application of a high voltage pulse thereto to cause an arc discharge between the trigger electrode and said cathode and an attendant substantially instantaneous initiation of an arc discharge with said anode, and a separate quantity of mercury in contact with said trigger electrode and with said cathode and constituting the surface thereof impinged by the arc discharge during operation, thus eliminating sputtering of electrode material otherwise occurring from the electrode surface impinged by the arc discharge with an attendant variation in the electrode spacings and operating characteristics which destroy the useful life of the device.

CLARENCE E. DAWLEY. 

